public static void IfCollectionContainsNull <T>( [CanBeNull, AssertionCondition(AssertionConditionType.IS_NOT_NULL)] IEnumerable <T> collection, [NotNull] string collectionName) where T : class { Fail.RequiresCollectionName(collectionName); Fail.IfArgumentNull(collection, nameof(collection)); Fail.IfTrue(collection.Contains(null), "Collection '{0}' contains null", collectionName); }